The invention relates to voltage inverters which operate under quasi-resonance and which include pulse width modulation regulation.
Such inverters are described in the French Patent Application filed on 26 August 1991 for "Process for regulation of a voltage inverter operating under quasiresonance" under the number 91 10 607. The subject of this patent application is a process for regulating a voltage inverter operating under quasi-resonance, including a monophase or polyphase bridge with controlled components operating in blocked/saturated mode and an oscillating circuit arranged on the DC voltage side and consisting of an inductance in series with the voltage source and a capacitor joined in parallel to the controlled-component bridge, in which pulse width modulation regulation is carried out, the sampling period for which is much greater than the resonance period of the oscillating circuit.
According to this process, the pulse width modulation control pulses are formed by series of sinusoidal arcs and the control transitions are to be effected at discrete times, namely the zero-crossings of these arcs.
This process makes it possible to separate the function of retention, by analog means, at high frequency of the short-circuits required for sustaining the oscillation, from the actual function of regulation of the load of the inverter. This allows the use of digital regulators operating at frequencies below the resonance frequency and which can take into account the characteristics of the load.
This process therefore allows the association of the advantages specific to resonance at high frequency, namely volume reduction and efficiency and those of numerical controls, namely flexibility of processing, adaptability and optimization.
Applications with high power can be envisaged. The greater the power, the lower is the switching frequency of the controlled components, owing to switching losses.